Optical disk and a recording/reproduction apparatus using multiple address block groups shifted oppositely with multiple address blocks and non-pit data

ABSTRACT

Address groups are composed of two of address blocks  16, 17, 18 , and  19 , where the address blocks  16, 17, 18 , and  19  are disposed in a sector address region  5  and include identifiable information of address numbers  13  and overlapping sequential numbers  14 . The address groups are disposed so that each group is alternately shifted from a track center  2  toward the inner periphery side or the outer periphery side, by a width substantially equal to half the track pitch, along the radius direction.

This is a continuation division of copending application Ser. No.09/171,044, filed Jan. 4, 1999 which is a 371 of PCT/JP97/01301 filedApr. 15, 1997.

TECHNICAL FIELD

The present invention relates to a recordable/reproducible optical disk,in which information pit arrays of sector addresses are disposed so asto wobble between a land track and a groove track; and an optical diskrecording/reproduction apparatus for performing recording and/orreproduction for the optical disk.

BACKGROUND ART

Optical disks have excellent removability/portability and random accessperformance. Therefore, it has become more and more prevalent to employoptical disks as memories in various information equipment fields, e.g.,personal computers. As a result, there has been an increasing demand forincreasing the recording capacitance of optical disks.

In general, guide grooves for tracking control purposes are formed onrewritable optical disks, so that data is recorded and reproduced byutilizing the guide grooves as tracks. In addition, a track is dividedinto a plurality of sectors for sector-by-sector management of data.Therefore, in the production of such disks, address information for eachsector is often formed in the form of pits while forming the guidegrooves.

In currently prevalent rewritable optical disks, tracks for recordingdata are either the grooves formed during the disk formation (grooves)or the interspaces between grooves (lands). On the other hand, opticaldisks of a land-groove recording type for recording data on both thegrooves and the lands have also been proposed.

FIG. 22 illustrates an exemplary optical disk of the land-grooverecording type. As used herein, the portions which are located closer tothe optical disk surface are referred to as “grooves”, whereas theportions which are located further away from the optical disk surfaceare referred to as “lands”, as shown in FIG. 22. It should be noted that“lands” and “grooves” are mere names; therefore, the portions which arelocated closer to the optical disk surface may be referred to as“lands”, while the portions which are located further away from theoptical disk surface may be referred to as “grooves”.

An optical disk of the land-groove recording type requires sectoraddresses for both the lands and the grooves. In order to facilitate theprocess of forming address pits on an optical disk, an intermediateaddress method has been studied in which address pits are formed betweena land and a groove adjoining each other so that the same address isshared by the adjoining tracks (Japanese Laid-Open Publication No.6-176404).

Hereinafter, the intermediate address, a tracking control method forreading information from an optical disk, and a method for readingsignals from an intermediate address will be described with reference tothe figures.

FIG. 23 is a schematic diagram showing an optical disk having a sectorstructure. In FIG. 23, reference numeral 200 denotes a disk; referencenumeral 201 denotes a track, reference numeral 202 denotes a sector;reference numeral 203 denotes a sector address region; and referencenumeral 204 denotes a data region. FIG. 24 is a magnified view of asector address region schematically showing a conventional intermediateaddress. In FIG. 24, reference numeral 206 denotes address pits;reference numeral 207 denotes recording marks; 208 denotes a groovetrack; reference numeral 209 denotes a land track; and reference numeral210 denotes a light spot.

In the optical disk shown in FIG. 24, the groove 208 and the land 209are employed as tracks. Data signals can be recorded by forming therecording marks 207 on the groove 208 and the land 209. The groove track208 and the land track 209 have the same track pitch Tp. The center ofeach address pit 206 is shifted by Tp/2 from the center of the groovetrack 208 along the radius direction. In other words, each address pit206 is centered around the boundary between the groove 208 and the land209. Although the lengths or intervals of the address pits 206 aremodulated by an address signal, FIG. 24 only schematically illustratesthe shapes of the address pits 206.

FIG. 25 is a block diagram showing the conventional tracking control andthe signal processing for reading signals on an optical disk.

The structure shown in FIG. 25 will be described below, In FIG. 25,reference numeral 200 denotes a disk; reference numeral 201 denotes atrack; reference numeral 210 denotes a light spot; and reference numeral211 denotes a disk motor for rotating the disk 200. An optical head 212optically reproduces a signal on the disk 200. The optical head 212includes a semiconductor laser 213, a collimation lens 214, an objectlens 215, a half mirror 216, photosensitive sections 217 a and 217 b,and an actuator 218. A tracking error signal detection section 220detects a tracking error signal indicating the amount of dislocationbetween the light spot 210 and the track 201 along the radius direction.The tracking error signal detection section 220 includes a differentialcircuit 221 and a LPF (low pass filter) 222. A phase compensationsection 223 generates a drive signal from a tracking error signal fordriving the optical head. A head driving section 224 drives the actuator218 in the optical head 212 in accordance with the drive signal.

An address reproduction section 234 includes an addition circuit 225, awaveform equalization section 226, a data slice section 227, a PLL(phase locked loop) 228, an AM detection section 229, a demodulator 230,a switcher 231, and an error detection section 232. The addition circuit225 adds signals from the photosensitive sections 217 a and 217 b. Thewaveform equalization section 226 prevents the inter-sign interferenceof a reproduced signal. The data slice section 227 digitizes thereproduced signal at a predetermined slice level. The PLL (Phase LockedLoop) 228 generates a clock which is in synchronization with thedigitized signal. The AM detection section 229 detects AMs (addressmarks). The demodulator 230 demodulates the reproduced signal. Theswitcher 231 separates the demodulated signal into data and an address.The error detection section 232 performs an error determination in theaddress signal. An error correction section 233 corrects errors in thedata signal.

Hereinafter, an operation for tracking control will be described. Laserlight radiated from the semiconductor laser 213 is collimated by thecollimate lens 214 and converged on the disk 200 via the object lens215. The laser light reflected from the disk 200 returns to thephotosensitive sections 217 a and 217 b via the half mirror 216, wherebythe distribution of light amount is detected as an electric signal,which is determined by the relative positions of the light spot 210 andthe track 201 on the disk. In the case of using the two-dividedphotosensitive sections 217 a and 217 b, a tracking error signal isdetected by detecting a difference between the photosensitive sections217 a and 217 b by means of the differential circuit 221 and extractinga low frequency component of the differential signal by means of the LPF222. In order to ensure that the light spot 210 follows the track 201, adrive signal is generated in the phase compensation section 223 suchthat the tracking error signal becomes 0 (i.e., the photosensitivesections 217 a and 217 b have the same distribution of light amount),and the actuator 218 is moved by the head driving section 224 inaccordance with the drive signal, thereby controlling the position ofthe object lens 215.

On the other hand, when the light spot 210 follows the track 201, theamount of reflected light is reduced at the recording marks 207 and atthe address pits 206 on the track owing to interference of light,thereby lowering the outputs of the photosensitive sections 217 a and217 b, whereas the amount of reflected light increases where pits do notexist, thereby increasing the outputs of the photosensitive sections 217a and 217 b. The total light amount of the output from thephotosensitive sections which corresponds to the recording marks 207 andaddress pits 206 is derived by the addition circuit 225, led through thewaveform equalization section 226 so as to remove the inter-signinterference of the reproduced signal, and digitized at a predeterminedslice level at the data slice section 227 so as to be converted into asignal sequence of “0” and “1”. Data and a read clock are extracted fromthis digitized signal by the PLL 228. The demodulator 230 demodulatesthe recorded data which has been modulated, and converts it into a dataformat which allows for external processing. If the demodulated data isa signal in the data region, the errors in the data are corrected in theerror correction section 233, whereby a data signal is obtained. On theother hand, if the AM detection section 229 detects an AM signal foridentifying the address portions in a signal sequence that is constantlyoutput from the PLL 228, the switcher 231 is switched so that thedemodulated data is processed as an address signal. The error detectionsection 232 determines whether or not the address signal which has beenread includes any errors; if no error is included, the address signal isoutput as address data.

FIG. 26 shows the states of a reproduced signal (RF signal) and atracking error signal (TE signal) when the light spot 210 passes thesector address region 203 in the above-described configuration. Althoughthe light spot 210 is on the center of the track in the data region 204,a drastic dislocation occurs between the light spot 210 and the addresspits 206 immediately after the light spot 210 enters the sector addressregion 203, thereby greatly fluctuating the level of the TE signal. Thelight spot 210 cannot rapidly follow the address pits but graduallycomes closer to the address pits, as indicated by the broken line.However, since the sector address region 203 is short and the dataregion 205 (which is a grooved region) is reached before the light spot210 manages to completely follow the address pits, a tracking control isperformed so that the off-tracking becomes zero in the grooved region.The amount of off-tracking in the last portion of the sector addressregion is defined as Xadr. Moreover, since a portion of the light spot210 is on the address pits 207, an RF signal as shown in FIG. 26 isobtained. The RF signal amplitude Aadr varies in accordance with thedistance between the light spot 210 and the address pits 206.Specifically, Aadr decreases as the distance becomes larger, andincreases as the distance becomes smaller.

DISCLOSURE OF THE INVENTION

In the case where the address pits of intermediate addresses areprovided in only one direction along the radial direction, the distancebetween the light spot and the address pits may also vary in the sectoraddress region in the case where the center of the light spot isdislocated from the center of the track in the data region. As a result,there is a problem in that, although the amplitude of the reproducedsignal in the address pit region will increase if the light spot isshifted closer to the address pits, the amplitude of the reproducedsignal in the address pit region will decrease if the light spot isshifted away from the address pits, thereby resulting in an insufficientreading of the address.

There is also a problem in that, since the synchronization of the readclock and the setting of the slice level for digitization are to beperformed in the beginning portion of an address region, thereproduction of the beginning portion must become stable; otherwiseproper demodulation cannot occur even if a reproduction signal isobtained elsewhere.

There is also a problem in that, since the light spot is dislocated fromthe address pits in the sector address region, a large fluctuation inlevel, which does not indicate the actual track offset amount, occurs inthe tracking error signal. Since the tracking control is performed byusing such a tracking error signal, a tracking offset may occur afterthe light spot has passed the sector address section.

There is also a problem in that, since the same address pits are readfor a land track and a groove track adjoining each other, it isimpossible to identify whether or not a track which is currently beingfollowed is a land track or a groove track.

In view of the above-mentioned problems, the present invention has anobjective of providing an optical disk having a novel address pitarrangement in sector address sections such that insufficient reading ofaddress signals due to tracking offset is reduced and the trackingoffset after passing a sector address is reduced, the optical diskfurther enabling identification of land tracks and groove tracks; anoptical disk recording/reproduction. apparatus employing such an opticaldisk; and an optical disk recording/reproduction apparatus including anID detection circuit for optical disks capable of accurately detectingthe locations and polarities of ID sections.

The optical disk recording/reproduction apparatus includes an apparatusfor recording data on an optical disk, an apparatus for reproducing datarecorded on an optical disk, and an apparatus for recording data on anoptical disk and reproducing data recorded on an optical disk.

The optical disk according to the present invention is a land-grooveoptical disk including a plurality of sectors having a sector addressand a data region, the sector address indicating a sector position,wherein the sector address includes a plurality of address blocks, atleast four of the plurality of address blocks each containing an addressnumber and an overlapping sequential number; each two of the at leastfour of the plurality of address blocks make a group; and the respectivegroups of address blocks are in an alternating arrangement from a trackcenter between being shifted toward an inner periphery side and towardan outer periphery side, by a width substantially equal to half a trackpitch, along a radius direction. As a result, the above-mentionedobjectives are met.

The sector address may include a block containing information other thanthe address number and the overlapping sequential number; and the blockmay be disposed so as to be shifted from the track center toward one ofthe inner periphery side and the outer periphery side, by the widthsubstantially equal to half the track pitch, along the radius direction.

The sector address may include at least two blocks containinginformation other than the address number and the overlapping sequentialnumber; and the blocks may be disposed so that one of the at least twoblocks is shifted from the track center toward the inner periphery side,and the other of the at least two blocks is shifted toward the outerperiphery side, by the width substantially equal to half the trackpitch, along the radius direction.

Preferably, a first pattern and a last pattern of each address blockincludes non-address pit data.

At least four of the plurality of address blocks may contain data of aclock synchronization signal; and data of the clock synchronizationsignal contained in a first address block of each group may have alength longer than lengths of the clock synchronization signalscontained in other address blocks of the group.

An optical disk recording/reproduction apparatus includes: an opticalhead for radiating a light beam on the aforementioned optical disk andreceiving reflected light therefrom to output a reproduced signal; anaddress signal reproduction section for reading the address numbers andthe overlapping sequential numbers when reproducing the sector addressesof the optical disk; and an address correction section for correcting,with respect to each address block, the address numbers which have beenread in accordance with the overlapping sequential numbers which havebeen read. As a result, the above-mentioned objectives are met.

Another optical disk recording/reproduction apparatus according to thepresent invention includes: the aforementioned optical disk; a trackingerror signal detection section for detecting a tracking error signalindicating an offset amount between a track and a light spot; a timinggeneration section for generating gate signals in synchronization withthe respective address blocks of the sector address; an outer peripheryvalue sample-hold section for sampling and holding, in synchronizationwith the gate signal, a level of the tracking error signal with respectto an address block disposed on the outer periphery side; an innerperiphery value sample-hold section for sampling and holding a level ofthe tracking error signal with respect to an address block disposed onthe inner periphery side; a differential circuit for deriving adifference in values of the outer periphery value sample-hold sectionand the inner periphery value sample-hold section; and gain conversionsection for converting the output of the differential circuit to apredetermined signal level. As a result, the above-mentioned objectivesare met.

Still another optical disk recording/reproduction apparatus according tothe present invention includes: the aforementioned optical disk; areflected light amount signal detection section for detecting areflected light amount from the optical disk; a timing generationsection for generating gate signals in synchronization with therespective address blocks of the sector address; an outer peripheryvalue sample-hold section for sampling and holding, in synchronizationwith the gate signal, a level of the reflected light amount signal withrespect to an address block disposed on the outer periphery side; aninner periphery value sample-hold section for sampling and holding alevel of the reflected light amount signal with respect to an addressblock disposed on the inner periphery side; a differential circuit forderiving a difference in values of the outer periphery value sample-holdsection and the inner periphery value sample-hold section; and gainconversion section for converting the output of the differential circuitto a predetermined signal level. As a result, the above-mentionedobjectives are met.

An optical recording/reproduction apparatus including an ID detectioncircuit for an optical disk according to the present invention includes:a tracking error detection circuit including split detectors forobtaining a tracking error signal for the aforementioned optical diskand a broad-band differential amplifier for outputting a differentialcomponent between detected signals from the split detectors as atracking error detection circuit; an envelope detection circuitincluding a high pass filter for extracting a high frequency componentof the tracking error signal, a full-wave rectifier for applyingfull-wave rectification to the high frequency component, a first lowpass filter for extracting a low frequency fluctuation component of thefull-wave rectified high frequency component, and a first comparator forcomparing the low frequency fluctuation component and a referencevoltage to output an ID envelope signal; a polarity detection circuitincluding a second low pass filter for extracting a second low frequencycomponent from the tracking error signal, a third low pass filter forextracting a third low frequency component from the tracking errorsignal, the third low frequency component having a smaller band widththan that of the second low frequency component, and a second comparatorfor comparing the second low frequency component and the third lowfrequency component to output an ID polarity signal; and a logic circuitfor outputting a read gate and a land-groove identification signal fromthe envelope signal and the polarity signal. As a result, theabove-mentioned objectives are met.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an optical disk according to Example1.

FIG. 2 is a diagram illustrating the format of sector addresses.

FIG. 3A is a diagram showing a portion of a data region and a sectoraddress region.

FIG. 3B is a diagram illustrating an RF signal and a TE signal in asector address region.

FIG. 4A is a diagram illustrating a tracking offset of a light spot andan RF signal.

FIG. 4B is a diagram illustrating a tracking offset of a light spot andan RF signal.

FIG. 5A is a diagram showing the arrangement of address blocks accordingto Example 2.

FIG. 5B is a diagram showing the arrangement of address blocks accordingto Example 2.

FIG. 6A is a diagram showing the arrangement of address blocks accordingto Example 3.

FIG. 6B is a diagram showing the arrangement of address blocks accordingto Example 3.

FIG. 7A is a schematic diagram illustrating continuous pits in addressgroups.

FIG. 7B is a schematic diagram illustrating continuous pits in addressgroups.

FIG. 8A is a diagram illustrating a reading operation for pits in thecase where a light spot is reproducing a land track.

FIG. 8B is a diagram illustrating a reading operation for pits in thecase where a light spot is reproducing a land track.

FIG. 9A shows an exemplary data waveform.

FIG. 9B shows an exemplary data waveform.

FIG. 9C shows an exemplary data waveform.

FIG. 9D shows an exemplary data waveform.

FIG. 10 is diagram illustrating data arrangement within an addressblock.

FIG. 11 is a diagram showing an exemplary case where address numbers areadded to sector addresses.

FIG. 12 is a block diagram showing an exemplary optical diskrecording/reproduction apparatus.

FIG. 13 is a block diagram showing an address correction section.

FIG. 14 is a block diagram showing an exemplary optical diskrecording/reproduction apparatus.

FIG. 15A is a schematic diagram showing the change in a tracking errorsignal (TE signal) in response to off-tracking in a sector addressregion 5.

FIG. 15B is a diagram showing a TE signal in the case where the. spotproceeds as (a) on a track 2.

FIG. 15C is a diagram showing a TE signal in the case where the spotproceeds as (b) on a track 2.

FIG. 15D is a diagram showing a TE signal in the case where the spotproceeds as (c) on a track 2.

FIG. 16A is a diagram showing a portion of a data region and a sectoraddress region.

FIG. 16B is a diagram of a timing chart illustrating the generation ofgate signals in a timing generation section.

FIG. 16C is a diagram of a timing chart illustrating the generation ofgate signals in a timing generation section.

FIG. 17 is a block diagram showing an optical diskrecording/reproduction apparatus according to Example 8.

FIG. 18 is a block diagram showing an optical diskrecording/reproduction apparatus including an ID detection circuit.

FIG. 19A is a diagram showing an ID section which is disposed in asymmetrical manner in a middle position between a land and a groove.

FIG. 19B is a diagram showing a tracking error signal obtained whenscanning with a light beam.

FIG. 19C is diagram showing a signal obtained after a tracking errorsignal has passed through a high pass filter.

FIG. 19D is a diagram showing a signal obtained by applying full-waverectification with a full-wave rectifier to a signal which has passedthrough a high pass filter.

FIG. 19E is a diagram showing a signal obtained after a full-waverectified signal has passed through a first low pass filter.

FIG. 19F is a diagram showing a signal which has passed through secondand third low pass filters.

FIG. 19G is a diagram showing an envelope signal in an ID section.

FIG. 19H is a diagram showing a polarity signal.

FIG. 20A is a diagram showing an ID section which is disposed in asymmetrical manner in a middle position between a land and a groove.

FIG. 20B is a diagram showing a tracking error signal obtained whenscanning with a light beam.

FIG. 20C is diagram showing a signal obtained after a tracking errorsignal has passed through a high pass filter.

FIG. 20D is a diagram showing a signal obtained by applying full-waverectification with a full-wave rectifier to a signal which has passedthrough a high pass filter.

FIG. 20E is a diagram showing a signal obtained after a full-waverectified signal has passed through a first low pass filter.

FIG. 20F is a diagram showing a signal which has passed through secondand third low pass filters.

FIG. 20G is a diagram showing an envelope signal in an ID section.

FIG. 20H is a diagram showing a polarity signal.

FIG. 21 is a diagram showing a logic circuit.

FIG. 22 is a diagram showing an exemplary optical disk of a land-grooverecording type.

FIG. 23 is a diagram showing the track structure of arecording/reproduction optical disk.

FIG. 24 is a schematic diagram showing a conventional sector address.

FIG. 25 is a block diagram showing a conventional optical diskrecording/reproduction apparatus.

FIG. 26 is a diagram illustrating an RF signal and a TE signal in aconventional example.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, examples of the present invention will be described withreference to the figures.

Example 1

FIG. 1 shows the outlook of an optical disk according to Example 1 ofthe present invention. In FIG. 1, reference numeral 1 denotes a disk;reference numeral 2 denotes a track; reference numeral 3 denotes asector address; reference numeral 4 denotes a sector; reference numeral5 denotes a sector address region; and reference numeral 6 denotes adata region.

In accordance with a predetermined physical format, a plurality ofsectors are successively disposed on a disk 1 along a track 2, eachsector defining one unit. Each sector 4 is composed of a sector addressregion 5 indicating the position of that sector on the disk and a dataregion 6 for actually recording data.

FIG. 2 shows an exemplary logical format of a sector address. A sectoraddress includes a plurality of address blocks. Each address block hasan address number and a overlapping sequential number. The addressnumber and the overlapping sequential number are composed ofidentifiable information. A value which is unique to each address blockis written to the overlapping sequential number.

In the present example, each sector address includes four address blockssharing the same format. The address blocks are indicated as ID1 to ID4,respectively, from the beginning of the sector address.

In FIG. 2, reference numeral 10 denotes a clock synchronization signal(VFO); reference numeral 11 denotes an address mark (AM); referencenumeral 12 denotes an overlapping sequential number (ID number);reference numeral 13 denotes the address number of the sector; referencenumeral 14 denotes an error detection code (EDC); and reference numeral15 denotes a postamble (PA). Reference numerals 16, 17, 18, and 19denote respective address blocks. Each address block includes the VFO10,the AM 11, the ID number 12, the address number 13, the EDC 14, and thePA 15.

In the VFO10, a clock synchronization signal is recorded which has acontinuous repetition pattern for ensuring secure reproduction of anaddress signal in spite of possible fluctuation in the disk rotation. Aclock for reading data is generated by locking a PLL (Phase Locked Loop)to this pattern. In the AM 11, an address mark composed of a specificcode pattern for indicating the start point of the address data isrecorded. In the ID number 12, a number (overlapping sequential number)which is unique to each address block is recorded. In the address number13, address data indicating some or all of the positions on the disk atwhich sectors corresponding to that address number are located isrecorded. In the EDC 14, an error detection code generated from anaddress number and an ID number is recorded. The PA 15 is a postamblefor ensuring that the last data of the error detection code conforms tothe rules of the modulation code during recording.

In the present example, each address block has the format shown in FIG.2. The address block according to the present invention can have anyformat as long as they contain the most indispensable information, e.g.an address number and an overlapping sequential number (ID number).Furthermore, the address block according to the present invention caninclude additional information as well as a clock synchronizationsignal, an address mark, an overlapping sequential number, an addressnumber, an error detection code, and a postamble as described above.

FIG. 3A shows the arrangement of address blocks in a sector addressregion. Reference numeral 5 denotes a sector address region, whereasreference numerals 6 and 7 denote data regions. Reference numerals 21and 23 denote groove tracks; reference numeral 22 denotes a land track;reference numeral 24 denotes a light spot; reference numeral 25 denotesan address pit; and reference numeral 26 denotes a recording mark. It isassumed that the track width of one track is Tp for both the land tracksand the groove tracks. It is assumed that the address blocks ID1 and ID2make one address group and that the address blocks ID3 and ID4 makeanother address group. Each address group is shifted from the trackcenter by Tp/2 along the radius direction. Specifically, one addressgroup is shifted by Tp/2 toward the center of the optical disk (innerperiphery), whereas the other address group is shifted by Tp/2 away fromthe center of the optical disk (outer periphery). Alternatively, the oneaddress group can be shifted by Tp/2 away from the center of the opticaldisk, whereas the other address group can be shifted by Tp/2 toward thecenter of the optical disk.

FIG. 3B shows the waveforms of a reproduction signal (RF signal) and atracking error signal (TE signal) obtained when the light spotreproduces a sector address section. In general, the amplitude of the RFsignal takes a value which is substantially in proportion with the areawhich the light spot 24 occupies in the address pit 25. For example,when the light spot 24 is at the center of the track, the light spot 24illuminates substantially the same area of the address pits 25 of theaddress blocks ID1 and ID2 as the area of the address pits 25 of theaddress blocks ID3 and ID4 that is illuminated. Thus, an RF signalhaving substantially the same amplitude can be obtained, as shown inFIG. 3B.

In the data regions 6 and 7 of grooves, the TE signal takes values whichare in proportion with the amount of offset between the light spot 24and the track groove. Similarly, in the sector address region 5 composedof pits, the TE signal takes values which are in proportion with theamount of offset between the light spot and the pits. Moreover, thepolarity of the TE signal changes depending on whether the pits 25 arelocated on the inner periphery side or the outer periphery side of thelight spot 24. Accordingly, the resultant TE signal has differentpolarities depending on the location of the address block as shown inFIG. 3B.

FIGS. 4A and 4B show the states of the RF signal in a sector addressregion when the light spot is in off-track states.

FIG. 4A shows the RF signal in the sector address region 5 in the casewhere the light spot 24 is shifted toward the inner periphery of thetrack. FIG. 4B shows the RF signal in the case where the light spot 24is shifted toward the outer periphery of the track. In FIG. 4A, the RFsignal has a large amplification in the address blocks ID1 and ID2 sincethe light spot 24 passes near the address blocks 16 and 17, and the RFsignal has a small amplification in the address blocks ID3 and ID4 sincethe light spot 24 passes at a distance from the address blocks 18 and19. Therefore, the address signal becomes difficult to read in ID3 andID4. However, at least one needs to be properly read in a sectoraddress. In the example shown in FIG. 4A, the RF signal corresponding toID1 and ID2 is large, thereby making it easy to read the address of ID1and ID2. Thus, the address of the sector address is read.

Similarly in FIG. 4B, the RF signal amplitude is small in ID1 and ID2,thereby making it difficult to read the address, but the RF signalamplitude is conversely large in ID3 and ID4, thereby making it easy toread the address. In other words, the address readability in the sectoraddresses does not decrease irrespective of whether the light spotbecomes off-track toward the inner periphery side or the outer peripheryside from the track center.

By disposing ID1 and ID2 in an alternating manner with respect to ID3and ID4, the address readability is not decreased for either the landtracks or the groove tracks.

Furthermore, as in FIG. 3B, the level of the TE signal alternatelyshifts, i.e., to be positive or negative, for every address group.However, by wobbling the address groups, the frequency of level shiftsincreases. Specifically, in view of the time period (100 μsec or less)usually required for passing through a sector address region, thefrequency of level shifts of the TE signal is 10 kHz or more, which isconsiderably higher than the control band in which the light spot canfollow the target track. Therefore, it is difficult to ensure that thelight spot responds to such level shifts of the TE signal. However,since the address groups are disposed so that each address group iswobbled by the same amount toward the inner periphery or the outerperiphery, the mean value of level shifts becomes substantially zero, sothat offsets of the light spot due to a DC component are unlikely tooccur. As a result, tracking offset immediately after passing throughthe sector address region is minimized, and the disturbance in thetracking control in a subsequent data region can be reduced.

Although the present example described a case where 4 address blocks areprovided for 1 sector address, there is no limitation as to thesenumbers. In the case where an even number of address blocks are disposedequally on the inner periphery side and the outer periphery side, thereis provided an effect of preventing disturbance in the tracking controlafter passing through an address. In the case where an odd number ofaddress blocks are provided, DC components due to the level shifts inthe TE signal are generated, but it has little influence because thefrequency of level shifts in the TE signal is higher than the trackingcontrol band. It is desirable to provide an even number of addressblocks equally on the inner periphery side and the outer periphery sidein terms of both address readability and tracking control stability.

Although four address blocks can be redundantly provided in the presentexample, it is not necessary for all the address numbers to be the sameas long as there is a correspondence between the sector address and theaddress numbers to be recorded in the respective address blocks .

Example 2

Hereinafter, Example 2 of the present invention will be described withreference to FIGS. 5A and 5B. Example 2 relates to an optical disk inwhich additional information other than address information is added toa sector address region 5.

FIGS. 5A and 5B show the arrangement of information blocks in sectoraddress regions. In FIGS. 5A and 5B, referential numerals 107, 108, and109 denote additional information blocks, where information which is notaddress number information is recorded. Address blocks 16, 17, 18, and19 each contain address information for identifying an address numberfrom an ID number.

The address blocks 16, 17, 18, and 19 are similar to those described inExample 1 as illustrated in FIG. 2.

The additional information blocks for recording additional informationare disposed so as to be shifted by a width of about Tp/2 along theradius direction, as in the case of the address blocks 16, 17, 18, and19 in Example 1.

In particular, in the case where the additional information is shortrelative to the address blocks, or where it is impossible to divide theadditional information, the additional information block 107 is disposedeither on the inner periphery side (shown within a dotted line) or theouter periphery side (shown within a solid line), as shown in FIG. 5A.

In the case where the additional information block is relatively long,the additional information can be divided into identifiable block units108 and 109 disposed in an alternating arrangement between being shiftedtoward the inner periphery side and toward the outer periphery side ofthe track, as shown in FIG. 5B. By adopting the above-mentionedconfiguration, it is possible to improve the readability of addressinformation and additional information against off-tracking, and thestability of tracking control during and after passing through a sectoraddress region, as in Example 1.

Although the additional information blocks are disposed at the rearmostend of each sector address region according to the present example, theadditional information blocks can also be disposed in another positionwithout undermining the effects attained according to the presentexample. Although the additional information block 108 on the innerperiphery side is read next to the address block 19 in FIG. 5B, Example2 can be modified so that the additional information block on the outerperiphery side is read next to the address block 19, after which theadditional information block on the inner periphery side can be read.

Example 3

Hereinafter, Example 3 of the present invention will be described withreference to FIGS. 6 to 9.

FIGS. 6A and 6B show the arrangement of address blocks in sector addressregions. In FIGS. 6A and 6B, reference numerals 110 and 112 denotegroove tracks; reference numeral 111 denotes a land track; referencenumerals 113, 114, 115, 116, 117, 118, 119, and 120 denote addressblocks; and reference numeral 24 denotes a light spot. In FIG. 6A, thegroove track (groove) 110 and the address blocks 113, 114, 115 and 116disposed on both sides thereof are formed. Then, after one turn of amaster disk, the groove track 112 and the address blocks 117, 118, 119and 120 disposed on both sides thereof are formed.

In Example 3, as shown in FIG. 6B, data is arranged on the disk in sucha manner that the last pattern in each address block is not pits andthat the beginning pattern in the next address block is also not pits.

In particular, non-pit data which is longer than the rotation accuracy(ΔX) during the cutting of the master disk is provided as the non-pitdata in the last pattern and the beginning pattern of an address block.

Below is the reason why data is arranged on the disk in such a mannerthat the last pattern in each address block is not pits and that thebeginning pattern in the next address block is also not pits.

First, a method for forming tracks and address pits will be brieflydescribed. In general, tracks and pits are formed by radiating cuttinglaser light onto a rotating master disk. A continuous groove is obtainedwhen the laser light is continuously radiated, which becomes a track(i.e., groove in the present example). By discontinuously radiatinglaser light by turning it on and off in accordance with a recordingsignal representing an address, pits are formed in the portionsirradiated by the laser light and address signals can be recorded. Inother words, in the case of a disk having sector addresses, tracks andaddresses are formed in each complete round of the disk by controllingthe radiation of the cutting laser light in the groove portions and theaddress pit portions while moving the cutting laser light along theradius direction by a track pitch for every turn of the master disk.

The wobbled addresses according to Examples 1 and 2 are also formed by amethod similar to the above-described method for forming tracks andaddress pits. Specifically, groove tracks (grooves) are formed by thelaser light, and the address pits are disposed in a split manner, i.e.,so as to be either on the inner periphery side or the outer peripheryside of the track. Therefore, in a sector address region, the cuttinglaser light is turned on or off while shifting the center of the cuttinglaser light for each address block by Tp/2 either toward the center ofthe optical disk or in the opposite direction of the center of theoptical disk.

FIGS. 7A and 7B are schematic diagrams showing a portion where twoaddress groups are connected to each other. Specifically, the figuresillustrate the case where address blocks share a continuous pit array.

FIG. 7A shows an expected pit configuration. The last pit of the addressblock 114 and the first pit of the address block 115 are formed at apredetermined distance away from the center of each address block. Sincethe address pits are formed while displacing the laser light at theaddress sections during the cutting of the master disk, in the casewhere pits are to be formed in a portion connecting the address block114 and the address block 115, the laser light also irradiates the diskwhile displacing the cutting laser along the radius direction. As aresult, incorrect pits are formed as shown in FIG. 7B, so that it isimpossible to reproduce proper data.

Since the rotation accuracy and the like of the master disk have somefluctuation, the positions of address blocks of the same ID number(e.g., address blocks 113 and 117 shown in FIG. 6A) do not necessarycoincide in position along the circumference direction. If theirpositions are offset by a distance of ΔX as shown in FIG. 6A, there is apossibility that the reproduced (RF) signal may not be accuratelydetected when reproducing the land track 111 because the end of theaddress block 118 and the beginning of the address block 115 overlapwith each other by the distance ΔX.

FIGS. 8A and 8B are diagrams illustrating a reading operation for pitsin the case where a light spot 24 is reproducing a land track 111. FIG.8A shows the address block 118 and the address block 115 in the casewhere the pit array in a connecting portion between address blocks isnot defined. Specifically, FIG. 8A shows the case where the addressblock 118 and the address block 115 overlap with each other in physicalterms and in term of timing at a cutting accuracy of ΔX, with thebeginning of the address block 115 being pit data.

In this case, if the non-pit data at the end of the address block 118overlaps with the pit data in the beginning of 115, the reproducedsignal which has been read from the disk will be determined asindicating the presence of pits, so that the data recorded in theaddress block 118 will not be properly reproduced.

FIG. 8B is a schematic diagram illustrating the case where the beginningand the end of the address block is non-pit data. When reproducing theaddress block 118 in FIG. 8B, if the non-pit data in the last data ofthe address block 118 overlaps with the non-pit data in the beginning ofthe address block 115, the reproduced signal will be non-pit data, sothat the data recorded in the address block 118 will be properlyreproduced. On the other hand, when reproducing the data recorded in theaddress block 115, the number of non-pit data in the beginning of theaddress block 115 cannot be properly read. However, in general, thebeginning of an address block is a VFO region, and it is not alwaysnecessary to reproduce all the data recorded in the VFO region becausethe problems inherent in the reading operation for address blocks can beavoided as long as synchronization can be reestablished in the AM regionfollowing the VFO region for reading the data recorded in the addressdata section so that the address number and the error detection code(EDC) can be properly recognized.

FIGS. 9A to 9D show exemplary data waveforms.

FIGS. 9A and 9B each show a VFO (clock synchronization signal) patternin the beginning of an address block. The code after recordingmodification is represented as NRZ (non return zero). The level of therecording signal is inverted at code “1”. The patterns in FIGS. 9A and9B show patterns which are inverted every 4T, where T represents theperiod of the recording codes. It is ensured that the beginning of thisrepetition pattern always begins with a space.

FIGS. 9C and 9D each show a postamble (PA) pattern in the end of anaddress block. In the postamble, the pattern in the earlier portion ofthe postamble varies depending on whether it follows a mark or a spacebecause the last data of the error detection code must conform to therules of modification code during recording. It is ensured that the restof the postamble to follow is always a space.

Thus, by ensuring that the beginning pattern and the last pattern ofeach sector address block are spaces as shown in FIGS. 9A to 9D, itbecomes possible to prevent, with respect to address blocks that aredisposed in a wobble manner, reading errors in address data due toincorrect formation of pits during the cutting of the master disk andoverlapping between address blocks during the reproduction of a sectoraddress. In the present example, errors do not occur even in the casewhere address blocks overlap with each other up to a length of 4T.

The method for forming grooves and address pits is not limited to thatdescribed above. As an alternative method, for example, a shift of onlyTp/2 can be effected per rotation of the master disk so as to form theaddress group on the inner periphery side, grooves, and the addressgroup on the outer periphery side in this order. In this case,malformation due to connections of pits does not occur because wobblingaddresses are cut in different rounds; however, overlapping of addressblocks may occur due to rotation accuracy errors. Accordingly, thestructure of the present example, where data is arranged on the disk insuch a manner that the last pattern in each address block is not pitsand that the beginning pattern in the next address block is also notpits, is effective. In this cutting method, one groove is formed perthree rotations.

Alternatively, it is possible to cut the track grooves, the address pitson the inner periphery side, and the address pits on the outer peripheryside with different lasers by employing a set of three laser beams,i.e., a laser beam for forming the track grooves, a laser beam forforming the address pits on the inner periphery side, and a laser beamfor forming the address pits on the outer periphery side, where therespective laser beams are turned on or off at predetermined positions.In this case, malformation due to connections of pits does not occurbecause wobbling addresses are cut in different rounds; however,overlapping of address blocks may occur due to laser positioningaccuracy errors. Accordingly, the structure of the present example,where data is arranged on the disk in such a manner that the lastpattern in each address block is not pits and that the beginning patternin the next address block is also not pits, is effective. This cuttingmethod employs a complicated cutting apparatus.

Example 4

Hereinafter, Example 4 of the present invention will be described withreference to FIG. 10.

FIG. 10 shows the arrangement of data in sector address blocks. As inExample 1, reference numerals 110 and 112 denote groove tracks;reference numeral 111 denotes a land track; reference numerals 113, 114,115, 116, 117, 118, 119, and 120 denote address blocks; and referencenumeral 24 denotes a light spot. The address block 113 in ID1 includesthe following data: VFO1, address mark (AM), ID number, address number,EDC, and postamble (PA). The address block 114 in ID2 includes thefollowing data: VFO2, address mark (AM), ID number, address number, EDC,and postamble (PA). ID3 and ID4 following ID1 and ID2 also includesimilar data. The order in which the respective data are arranged withineach address block is the same as in Example 1.

The difference from Example 1 is that the length of VFO1 of the addressblock in ID1 and ID3 is larger than that of VFO2 of the address block inID2 and ID4.

When a sector address region is reproduced with a light spot 24, thedata recorded in the address blocks in ID1 and ID2 are reproduced inthis order.

A data region 6 is composed of a track, but a sector address region 5 iscomposed of a mirror face having address pits formed therein, the mirrorface being shifted from the track center by Tp/2. Therefore, as shown inFIG. 4, the d.c. signal component (DC level) of the RF signal as areproduced signal in the data region 6 differs from the d.c. signalcomponent (DC level) of the RF signal in the sector address region 5.Thus, the level of the RF signal drastically changes immediately afterthe light spot 24 has moved from the data region 6 to the sector addressregion 5. Therefore, it takes more time to lock the PLL in order tomatch the phases of the data (VFO1) and the data reading clock used whenthe recording/reproduction apparatus reads the data recorded in ID1 thanin the case where there is no level variation. However, when the lightspot 24 travels from ID1 to ID2, the level of the RF signal does notchange, so that the time for locking the PLL in order to match thephases of the data (VFO2) and the data reading clock used when therecording/reproduction apparatus reads the data recorded in ID2 becomesshorter than in the case where there is some level variation. As aresult, the length of VFO2 can be made shorter than the length of VFO1.

When reproducing the sector address region of a land track, the phasesof the reproduction clocks for the former address group (ID1, ID2) donot necessarily coincide with those for the latter address group (ID3and ID4). This is because the former address group is recordedconcurrently with the groove adjoining the land track on the outerperiphery side, whereas the latter address group is recordedconcurrently with the groove adjoining the land track on the innerperiphery side, so that rotation variation and/or frequency variationmay occur between forming the groove on the outer periphery side andforming the groove on the inner periphery side. Therefore, therecording/reproduction apparatus relocks the PLL at the VFO1 of thefirst address block (ID3) of the latter address group. A longer lengthof VFO1 provides more stable locking.

In the case where the data lengths of all the address blocks are madeequal, the lengths of the VFO2s in ID2 to ID4 can be made equal to thelength of VFO1 required for the recording/reproduction apparatus toproperly reproduce the data recorded in ID1 and ID3. However, thismethod makes VFO2 in ID2 to ID4 unnecessarily long, and a lengthy VFO2leads to waste.

Therefore, the length of VFO2 in ID2 and ID4 can be made shorter thanthe length of VFO1 in ID1 and ID3, as long as a VFO length required foreach address block is secured. As a result, it becomes possible toreduce redundant data while maintaining readability of addresses.

By prescribing the length of VFO1 in ID1 and the length of VFO1 in ID3to be equal and prescribing the length of VFO2 in ID2 and the length ofVFO2 in ID4 to be equal, the date lengths in the address groups allbecome equal, and there is substantially no influence on the averagevalue of the tracking error signal in the sector address region asdescribed in Example 1.

Example 5

Hereinafter, Example 5 of the present invention will be described withreference to FIG. 11.

FIG. 11 shows an example where address numbers are assigned to thesector addresses of the disk described in Example 1. Reference numeral 5denotes a sector address region; reference numerals 6 and 7 denote dataregions; reference numerals 51, 53, 61, and 63 denote groove tracks;reference numerals 52 and 62 denote land tracks; and reference numerals54, 55, 56, 57, 64, 65, 66, and 67 denote address blocks.

A method for setting the addresses used in the present example will bedescribed. It is assumed that an address to be recorded in a sectoraddress region 5 represents the sector of a subsequent data region 7. Itis also assumed that groove tracks and land tracks alternate track bytrack, with sector addresses sequentially assigned thereto. Only theaddress values of a sector of a groove are set in a set of addressblocks (ID1 to ID4), so that the same value is repetitively recorded.Assuming that the sector address of the groove track 61 is #n, thesector address of the groove track 51 is #(n−1). As the address valuefor the address blocks 54, 55, 56, and 57, #n is recorded in eachaddress region (address 13 in FIG. 2). It is assumed that the land track52 is #(n+k−1); the land track 62 is #(n+k); the groove track 53 is#(n+2k−1); and the groove track 63 is #(n+2k), where the track number iscounted up by k for every turn of a track. As an address value for theaddress blocks 64, 65, 66, and 67, #(n+2k) is recorded.

Example 6

FIG. 12 is a block diagram showing an optical diskrecording/reproduction apparatus according to Example 6 for reading outthe sector address of the optical disk described in Example 1. In FIG.12, reference numeral 31 denotes a disk; reference numeral 32 denotes adisk motor; reference numeral 33 denotes an optical head; and referencenumeral 34 denotes an address reproduction section. The addressreproduction section 34 includes an addition circuit 35, a waveformequalization section 36, a data slice section 37, a PLL 38, ademodulator 39, an AM detection section 40, a switcher 41, and an errordetection section 42. Reference numeral 43 denotes an error correctionsection; and reference numeral 44 denotes an address correction section.

Although a process for controlling the position of the light spot alongthe focus direction is performed, the present invention assumes that ageneral focusing control is implemented, and therefore the descriptionof focusing control is omitted.

Hereinafter, an operation of the optical disk recording/reproductionapparatus of FIG. 12 for reading the data recorded in a sector addressregion including address blocks arranged as shown in FIG. 11 will bedescribed.

An optical head 33 radiates laser light onto the disk 31, whereby tworeproduced signals are detected from the amount of reflected light fromthe disk 31. The two reproduced signals are added by the additioncircuit 35 to give an RF signal, and the RF signal is led through thewaveform equalization section 36, the data slice section 37, the PLL 38,the demodulator 39, the switcher 41, and the error detection section 42,and an address number and an ID number are extracted for each addressblock. The operation of extracting the address number and the ID numberis the same as that illustrated in the description of conventionalexamples.

When the light spot 24 reproduces the groove tracks 51 to 61, theaddress signals obtained in the sector address region are, respectively,(#n, 1), (#n, 2), (#n, 3), and (#n, 4), which are pairs of (addressnumber, ID number). These values are input to the address correctionsection 44 (see FIG. 13).

On the other hand, when the light spot 24 reproduces the groove tracks52 to 62, the address signals obtained in the sector address region are,respectively, (#n+2k, 1), (#n+2k, 2), (#n, 3), and (#n, 4), which areinput to the address correction section 44 in this order.

In the address correction section 44, the address value of the sector isdetermined based on the pair of the reproduced address number and IDnumber. The determination utilizes the rules of a format in which anaddress value is assigned to each address block. In the present example,the format shown in FIG. 11 is employed. According to such a definition,all of the four reproduced addresses take the same value when a groovesector has been reproduced, whereas the address values within an addressgroup become the same when a land sector has been reproduced. Thedifference in address value between address groups is 2k, which is thenumber of sectors corresponding to two rounds of the track.

FIG. 13 shows the structure of an address correction section accordingto one example. In FIG. 13, reference numerals 71, 72, 73, and 74 denotememories; reference numerals 75 and 76 denote comparators; referencenumeral 77 denotes a determination circuit; reference numerals 78denotes an adder; reference numeral 79 denotes a divider. The addressnumber and ID number which have been determined to include no errors inthe error detection section 42 shown in FIG. 12 are sent to the addresscorrection section 44. In the address correction section in FIG. 13, theaddress numbers reproduced in the respective IDs are stored in thememories 71, 72, 73, and 74 corresponding to the respective ID numbers.The comparator 75 compares the address numbers from ID1 and ID2 storedin the memories 71 and 72. If they coincide, the address number isdetermined as being properly reproduced, and a “coinciding” signal isoutput to the determination circuit, and the address number is sent tothe adder 78.

Similarly, the comparator 76 compares the address numbers from ID3 andID4 stored in the memories 73 and 74. If they coincide, the addressnumber is determined as being properly reproduced, and a “coinciding”signal is output to the determination circuit, and the address number issent to the adder 78. The adder 78 adds the two address numbers, whichare sent to the divider 79. The divider 79 divides the input value by 2,and outputs this as a detected address number. The determination circuit77 determines whether the address number obtained is correct or notbased on the “coinciding” signals from the comparators 75 and 76.

A method for reading the data recorded in a sector address regionincorporating the address blocks shown in FIG. 11 will be described.When the light spot 24 reproduces the groove tracks 51 to 61, theaddress numbers obtained in the sector address region are, respectively,(#n, 1), (#n, 2), (#n, 3), and (#n, 4), which are pairs of (addressnumber, ID number). Thus, all the address values coincide, so that thedetermination circuit 77 recognizes it as the correct address, and theabove-described mathematical operation is performed for the addressvalue, whereby #n is obtained as a sector address. When the light spot24 reproduces the land tracks 52 to 62, the address numbers obtained inthe sector address region are, respectively, (#n+2k, 1), (#n+2k, 2),(#n, 3), and (#n, 4). The comparators 75 and 76 each output a“coinciding” signal. The determination circuit 77 determines it as thecorrect address, and the above-described mathematical operation isperformed for the address value, whereby #(n+k) is obtained as a sectoraddress.

According to the present example, it is unnecessary to identify a sectoras that of a groove or a land, so that a sector address can be alwaysobtained by the same mathematical operation.

However, the address correction method according to the present exampleis also applicable to the case where it is necessary to identify theaddresses of grooves from the addresses of lands due to, for example,system controls. The address numbers output from the comparators 75 and76 are also supplied to the determination circuit 77, where they arecompared for coincidence. The determination circuit 77 determines thatthe addresses represent a sector of a groove if they coincide, or thatthe addresses represent a sector of a land if they do not coincide. Amore strict determination can be achieved by the determination circuit77 comparing the two address numbers and determining them as pertainingto a sector of a land if the difference is 2k.

Although the present example described the case where all the addressblocks of ID1 to ID4 are reproduced without errors, the invention is notlimited thereto. In the case where an error is detected in the errordetection section 42, for example, even if a signal from a comparatorindicates “not coinciding”, the address of one address block of the sameaddress group which has been reproduced without errors can be adopted asan address number.

Furthermore, although it is ensured that the same address number can beread when reproducing a groove in the present example, it is alsoapplicable to ensure that the same address number can be read whenreproducing a land. Although the same address number is repeatedlyprovided for one set of address blocks (ID1 to ID4) of a groove track,the invention is not limited thereto. Instead of employing theabove-described recording format (rules) for the address, if the IDnumbers and their recording format (rules) are known, an address numbercan be generated based on the ID numbers and their recording format(rules).

Example 7

Example 7 of the present invention will be described with reference toFIGS. 14, 15A to 15D, and 16A to 16C. Example 7 relates to an apparatusfor detecting tracking offset of a light spot.

FIG. 14 is a block diagram showing the optical diskrecording/reproduction apparatus according to Example 7. In FIG. 14,reference numeral 31 denotes a disk; reference numeral 32 denotes a diskmotor; reference numeral 33 denotes an optical head; reference numeral34 denotes an address reproduction section; reference numeral 81 denotesa tracking error signal detection section. The tracking error signaldetection section 81 includes a differential circuit 82 and a LPF (LowPass Filter) 83. Reference numeral 84 denotes a phase compensationsection; reference numeral 85 denotes a head driving section; referencenumeral 90 denotes a timing generation section; reference numeral 91denotes an outer periphery value sample-hold section; reference numeral92 denotes an inner periphery value sample-hold section; referencenumeral 93 denotes a differential circuit; and reference numeral 94denotes a gain conversion circuit.

Hereinafter, an operation of the optical disk recording/reproductionapparatus of FIG. 14 for detecting an amount of offset between a lightspot and a track (off-tracking amount) in a sector address region havingaddress blocks disposed as shown in FIG. 10 will be described.

An optical head 33 radiates laser light onto the disk 31, whereby tworeproduced signals are detected from the amount of reflected light. Thetwo reproduced signals are converted by the address reproduction section34 into an RF signal, and an address number and an ID number areextracted from the RF signal for each address block; this operation isthe same as the operation in the description of conventional examples.The differential circuit 82 derives a difference between the reproducedsignals, and the derived difference is led through the LPF 83 so as tobe output as a TE signal.

FIG. 15A is a schematic diagram showing the change in the tracking errorsignal (TE signal) in a sector address region 5 during an off-trackstate. The level of the TE signal shifts substantially in proportionwith the distance between the light spot and the address block, and thedirection of level shifts is determined by the distance between thelight spot and the address block, as described in Example 1. Herein, itis assumed that the TE signal takes a negative value when the light spot24 passes on the outer periphery side of the address block and takes apositive value when the light spot 24 passes on the inner periphery sideof the address block. When the light spot 24 follows (a) of a track 2,the level shift VTE1 of the TE signal takes a small negative valuebecause the distance between the light spot 24 and the address block issmall in ID1 and ID2. The level shift VTE3 of the TE signal takes alarge positive value because the distance between the light spot 24 andthe address pits block is large in ID3 and ID4. As a result, a TE signalshown in FIG. 15B is obtained.

When the light spot 24 follows line (b) of the track 2, the level shiftamount is the same because the distances between the light spot 24 andthe address blocks ID1 to ID4 are the same. The level shift VTE1 takes anegative value in ID1 and ID2, and the level shift VTE3 takes a positivevalue in ID3 and ID4. As a result, a TE signal shown in FIG. 15C isobtained. When the light spot 24 follows line (c) of the track 2, thelevel shift VTE1 of the TE signal takes a large negative value becausethe distance between the light spot 24 and the address block is large inID1 and ID2. When the light spot 24 follows line (c) of the track 2, thelevel shift VTE3 of the TE signal takes a small positive value becausethe distance between the light spot 24 and the address block is large inID3 and ID4. As a result, a TE signal shown in FIG. 15D is obtained.

As shown in FIGS. 15A to 15D, the levels of VTE1 and VTE3 vary dependingon which position of the track 2 the light spot 24 has moved over, sothat the off-tracking amount can be deduced based on a differencebetween these level shifts, that is, by deriving Voftr=VTE1−VTE3. If thelight spot 24 follows the center line (b) of the track 2, VTE1−VTE3=0 inthe sector address region 5; if the light spot 24 follows the line (a)of the track 2, VTE1−VTE3 <0 in the sector address region 5; and if thelight spot 24 follows the line (c) of the track 2, VTE1−VTE3 >0 in thesector address region 5. Thus, the direction and amount of off-trackingcan be obtained.

Hereinafter, the operation of the timing generation section 90 forgenerating a timing signal for sampling the TE signal will be described.FIG. 16A is a diagram showing a portion of the data region and a sectoraddress region. FIGS. 16B and 16C are timing diagrams of gate signalgeneration in the timing generation section 90. Address read-out signalsare input from the address reproduction section 34 to the timinggeneration section 90. A gate signal GT1 which is in synchronizationwith address blocks on the inner periphery side and a gate signal GT2which is in synchronization with address blocks on the outer peripheryside are generated based on the address read-out signals. The gatesignal GT1 is a signal for sampling the TE signal in the inner peripheryvalue sample-hold section. The gate signal GT2 is a signal for samplingthe TE signal in the outer periphery value sample-hold section.

FIG. 16B shows exemplary gate signals GT0, GT1, and GT2 where therecording/reproduction apparatus of Example 7 has successfully read ID1.The timing with which ID2, ID3, and ID4 appear can be known if ID1 issuccessfully read. For example, the recording/reproduction apparatus ofExample 7 can generate the signal GT0, which is in synchronization withthe end of ID1. In the case where the signal GT0 in synchronization withthe end of ID1 is generated, the gate signal GT1 is generated at a pointlagging by time T1 behind the time at which the gate signal GT0 wasgenerated, and the gate signal GT2 is generated at a point lagging bytime T2 behind the time at which the gate signal GT0 was generated.Thus, the gate signal GT1 for sampling and holding the TE signal in theaddress block ID2 on the inner periphery side and the signal GT2 forsampling and holding the TE signal in the address block ID3 (or ID4;this example conveniently illustrates ID3) on the outer periphery sidecan be generated.

FIG. 16C shows an exemplary gate signal GT0 which is in synchronizationwith and represents a sector address region and also shows gate signalsGT1 and GT2 which are in synchronization with the gate signal GT0.

It is assumed that the gate signal GT0 representing a sector addressregion rises immediately before a sector address region. The gate signalGT1 is generated at a point lagging by time T3 behind the time at whichthe gate signal GT0 was generated. The gate signal GT2 is generated at apoint lagging by time T4 behind the time at which the gate signal GT0was generated. Thus, the gate signal GT1 for sampling and holding the TEsignal in the address block ID2 on the inner periphery side and thesignal GT2 for sampling and holding the TE signal in the address blockID3 (or ID4; this example conveniently illustrates ID3) on the outerperiphery side can be generated.

By using the gate signals GT1 and GT2 generated by the timing generationsection 90, with reference to FIG. 16B, for example, the level VTE3 ofthe TE signal in the address block ID3 on the outer periphery side isstored in the outer periphery value sample-hold section 91 insynchronization with the gate signal GT2, and the level VTE1 of the TEsignal in the address block ID2 on the inner periphery side is stored inthe inner periphery value sample-hold section 92 in synchronization withthe gate signal GT1. As a result, a value (VTE1−VTE3) is output from thedifferential circuit 93. Since this value corresponds to theoff-tracking amount, it can be further converted into an off-tracksignal (OFTR signal) by adjusting its level to the level of the TEsignal in the gain conversion section 94. In the tracking controlsystem, a state may occur in which the light spot is not actually in thetrack center while the TE signal is controlled to be zero, owing tooffset components and the like generated in the tracking error signaldetection section 81, the phase compensation section 84, and the headdriving section 85. Accordingly, by arranging the recording/reproductionapparatus having the structure shown. in FIG. 14 so that it generatesthe OFTR signal for correcting the offset in the tracking controlsystem, it becomes possible to position the light spot in the trackcenter. It is also possible to position the light spot in the trackcenter by using the gate signals GT0, GT1, and GT2 shown in FIG. 16C.

The gate signal GT1 is to be generated in synchronization with anaddress block on the inner periphery side, and the gate signal GT2 is tobe generated in synchronization with one of the address blocks on theouter periphery side. The gate signals GT1 and GT2 are not limited tospecific address blocks.

Although time T1 and time T2 do not need to be exactly timed, it ispreferable that the pit arrangement patterns in the respective addressblocks are measured with the same period. For example, in the addressblock format shown in FIG. 10, the clock synchronization signal (VFO1)of the address blocks ID1 and ID3 are prescribed to be very longrelative to the other regions, so that this region is suitably used forsampling because the reproduced signal becomes stable in this region (inparticular the latter portion).

Although one address block on the inner periphery side and one addressblock on the outer periphery side are sampled and held in the presentexample, a more averaged value can be detected by detecting an off-tracksignal using a mean value of a plurality of address blocks on the innerperiphery side and a mean value of a plurality of address blocks on theouter periphery side, even if the tracks are locally warped.

Example 8

Example 8 of the present invention will be described with reference toFIG. 17.

FIG. 17 is a block diagram showing the optical diskrecording/reproduction apparatus according to Example 8. In FIG. 17,reference numeral 31 denotes a disk; reference numeral 32 denotes a diskmotor; reference numeral 33 denotes an optical head; reference numeral34 denotes an address reproduction section; reference numeral 81 denotesa tracking error signal detection section; reference numeral 84 denotesa phase compensation section; and reference numeral 85 denotes a headdriving section. Reference numeral 90 denotes a timing generationsection; reference numeral 91 denotes an outer periphery valuesample-hold section; reference numeral 92 denotes an inner peripheryvalue sample-hold section; reference numeral 93 denotes a differentialcircuit; and reference numeral 94 denotes a gain conversion circuit.Reference numeral 100 denotes a reflected light amount signal detectionsection. The reflected light amount signal detection section 100includes an addition circuit 101 and a LPF (low pass filter) 102.

In FIG. 17, reference numerals 31, 32, 33, 34, 81, 84, 85, 90, 91, 92,and 93 denote the same constitution as that of Example 7, and thedescriptions of their operations are omitted. While a TE signal issampled and held in order to detect an off-tracking amount in Example 7,the detection of the off-tracking amount in Example 8 is performed bysampling and holding a reflected light amount signal (AS signal)detected by the reflected light amount signal detection section 100.

In the reflected light amount signal detection section 100, the outputsof a two-divided photosensitive elements of the optical head 33 aresummed up in the addition circuit 101, and the added signal is ledthrough the LPF 102 (having a band on the order of a few dozen kHz,which is higher than the tracking control band but lower than the RFsignal) in order to remove the high-frequency component thereof. As aresult, an AS signal is detected as a signal indicating an averagereflected light amount.

As described in Example 1, the RF signal shifts as shown in FIGS. 3B, 4Aor 4B depending on where the light spot 24 passes. FIG. 4A shows an RFsignal in the case where the light spot 24 passes along positionsshifted toward the inner periphery side, and FIG. 4B shows an RF signalin the case where the light spot 24 passes along positions shiftedtoward the outer periphery side.

Since the AS signal indicates an average level of the RF signal, the ASsignal varies so as to follow the change in amplitude of the RF signal.Therefore, by sampling and holding the AS signal in synchronization withthe address blocks on the inner periphery side and the address blocks onthe outer periphery side and obtaining a difference therebetween as inExample 7, a signal corresponding to the off-tracking amount can bedetected. Gate signals GT1 and GT2 for the sampling and holding aregenerated by the timing generation section 90 in Example 7. However, asfor the timing of gate pulse signal generation, it is preferable toemploy an AS signal derived from the VFO portion, the AM portion, or aspecially provided pit portion because a more accurate detection will beenabled by sampling AS signals at portions in address blocks having thesame pit pattern.

Moreover, the optical disk recording/reproduction apparatus of Example 8can employ an offtrack signal (OFTR signal) detected by using the ASsignal for correcting the offset in the tracking control system, as inExample 7.

Example 9

Hereinafter, an optical disk recording/reproduction apparatus accordingto Example 9 of the present invention will be described with referenceto FIGS. 18, 19A to 19H, 20A to 20H, and 21. The optical diskrecording/reproduction apparatus of Example 9 includes an ID detectioncircuit for an optical disk.

As shown in FIG. 19A, an optical disk to be used in Example 9 has astructure in which ID sections are provided in a symmetrical manner in amiddle position between a land and a groove. Alternatively, the IDsection may have a structure shown in FIG. 3A Example 9 provides afunction of detecting the positions and polarities of the ID sectionsbased on a reproduced signal from an optical disk and outputting a readgate and a land groove identification signal, which serve as referencesfor reading signals in the optical disk apparatus.

FIG. 18 is a block diagram showing an optical diskrecording/reproduction apparatus having an ID detection circuit for anoptical disk, illustrated as Example 9 of the present invention. In FIG.18, a tracking error detection circuit 101 receives a light beam 103reflected from an optical disk (not shown). The tracking error detectioncircuit 101 includes split detectors 102 for detecting trackinginformation and a differential amplifier 104 (which functions in a broadband width) for outputting a differential component between the detectedsignals from the respective split detectors 102 as a tracking errorsignal 105. The tracking error signal 105 is input to an envelopedetection circuit 106 and a polarity detection circuit 122. The envelopedetection circuit 106 includes: a high pass filter 107 for extracting ahigh frequency component of the tracking error signal 105; a full-waverectifier 109 for subjecting the high frequency component 108 tofull-wave rectification; a first low pass filter 111 for extracting alow frequency fluctuation component 112 from the high frequencycomponent 110 which has been full-wave rectified; and a first comparator114 for comparing the low frequency fluctuation component 112 and areference voltage 113 and outputting an ID envelope signal 115. Thepolarity detection circuit 122 includes: a second low pass filter 116for extracting a second low frequency component 117 from the trackingerror signal 105; a third low pass filter 118 for extracting a third lowfrequency component 119 from the tracking error signal 105, the thirdlow frequency component 119 having a smaller band width than that of thesecond low frequency component; and a second comparator 120 forcomparing the second low frequency component 117 and the third lowfrequency component 119 and outputting an ID polarity signal 121.

FIGS. 19A to 19H are signal waveform diagrams illustrating theoperations of the respective sections according to Example 9. Theoperation according to Example 9 will be described with reference toFIGS. 19A to 19H.

FIG. 19A is a diagram schematically showing a light beam scanning over agroove track of an optical disk for reproducing the groove track. The ∘symbol in FIG. 19A represents the light beam, and the hatched portionsrepresent grooves. The ID sections are provided in a symmetrical mannerin a middle position between a land and a groove and inserted in betweentracks.

FIG. 19B is a diagram showing the tracking error signal 105 obtained byscanning with the light beam. The tracking error signal 105 is obtainedby reproducing the signal pits in an ID section as a high frequencycomponent by using the broad-band differential amplifier 104. As for anysignal recorded in the groove portions other than the ID sections, thedetected components from both split detectors have the same phase, sothat the recorded signal is cancelled in the differential amplifier 104and cannot be detected as a tracking error signal.

FIG. 19C shows a signal obtained after the tracking error signal 105 haspassed through the high pass filter 107. The tracking error signal 105is input to the high pass filter 107, and the high frequency component108 of the tracking error signal 105 is output as shown in FIG. 19C. Atthis time, the gap in the tracking error signal between the ID sections,i.e., the d.c. component, and the low frequency fluctuation occurringdue to servo disturbance are removed by the high pass filter 107.

FIG. 19D shows a signal obtained by applying full-wave rectificationwith the full-wave rectifier 109 to the signal which has passed throughthe high pass filter 107. The high frequency component is full-waverectified in the full-wave rectifier 109 and input to the first low passfilter 111.

FIG. 19E shows a signal obtained after the full-wave rectified signalhas passed through the first low pass filter 111. The low frequencyfluctuation component 112 which has been smoothed by the first low passfilter 111 is digitized by the first comparator 114 based on itsrelationship with the reference voltage 113 shown in FIG. 19E, so thatthe ID envelope signal 115 as shown in FIG. 19G is generated.

On the other hand, the tracking error signal 105 is input to the secondlow pass filter 116 and the third low pass filter 118, whereby thesecond low frequency component 117 and the third low frequency component119 are respectively extracted. As shown in FIG. 19F, the gap in thetracking error signal between the ID sections, i.e., the d.c. component,remains intact in the extracted waveform, and due to the difference inthe bands of the second and third low pass filters, the amplitude of thesecond low frequency component 117 always exceeds the amplitude of thethird low frequency. component 119. Furthermore, this relationship inamplitude is always true even if the reproduction light beam is in anoff-track state. Accordingly, the ID polarity signal 121 indicating achange in the position of the ID section is output by the secondcomparator 120 comparing the second low frequency component signal 117and the third low frequency component signal 119 (FIG. 19H). In thisexample, a falling edge is detected as a polarity signal in a periodduring which the envelope signal is valid.

Hereinafter, a polarity signal obtained in the case where the light beamis scanning over a land track of an optical disk in order to reproducethe land track will be described.

FIG. 20A is a diagram schematically showing the case where the lightbeam is scanning over a land track of an optical disk in order toreproduce the land track. The description concerning the same operationas the above-described operation of scanning a groove track to obtain apolarity signal in Example 9 is omitted.

The case of land track scanning differs from the case of groove trackscanning in the position of the gap in the tracking error signal shownin FIG. 20B (phase of the tracking error signal), and in the phases ofthe signals which are output from the second and third low pass filtersshown in FIG. 20F. As in the case of scanning a groove track to obtain apolarity signal, Example 9 provides for the detection of a rising edgein a period during which the envelope signal is valid as a polaritysignal.

Below are some desirable parameters in the implementation of theenvelope detection circuit 106 and the polarity detection circuit 122 ofExample 9. Experiments were conducted under conditions where thereproduction linear speed for the optical disk was 6 m/s; the data ratewas 14 Mbps; and the ID period was 0.4 mm. The envelope signal 115 wasaccurately detected in the case where the high pass filter 107 had acut-off frequency of about 1 MHz and the first low pass filter had acut-off frequency of about 100 KHz , in spite of any dropouts (i.e.,minute losses of the signals). Under the same conditions, the detectionerror of the polarity signal 121 became zero by ensuring that the secondand third low pass filters had an about tenfold band difference wherethe cut-off frequency of the second low pass filter was about 10 KHz andthe cut-off frequency of the third low pass filter was about 10 KHz.Thus, excellent detection results were obtained with respect to offsetsof the light beam.

A specific example of a logic circuit shown in FIG. 21 will bedescribed. The input signals to the logic circuit 131 are theabove-described envelope signal 115 and the polarity signal 121, and theoutput signals are the read gate 127 and a land-groove identificationsignal 128. The polarity signal 121 is input to a falling edge detectioncircuit 130 and a rising edge detection circuit 123, and these circuitsoutput edge pulses. An AND gate 124 extracts the edge pulses only whenthe envelope signal 115 is valid. The extracted edge pulses are input toan RS flip-flop 125. The RS flip-flop 125 outputs the land-grooveidentification signal 128.

Hereinafter, a method for identifying lands from grooves will bedescribed.

When a groove is being tracked, a falling edge of the polarity signal121 is detected in a period during which the envelope signal 115 and areset signal is input to the RS flip-flop 125 so that the land-grooveidentification signal 128 shifts to a LO level.

On the other hand, when a land is being tracked, a rising edge of thepolarity signal 121 is detected in a period during which the envelopesignal 115 and a set signal is input to the RS flip-flop 125 so that theland-groove identification signal 128 shifts to a HI level.

Thus, the detection as to land-groove is possible in accordance with theHI/LO levels of the land-groove identification signal. A delay 126 andan AND gate 129 remove the unnecessary pulse noise from the envelopesignal 115, thereby generating the read gate 127, which serves as asignal reading reference for the optical disk drive apparatus.

The logic circuit is not limited to the circuit described above, but canhave functions of pattern matching or error detection protection forgenerating a read gate and a land-groove identification signal based onan ID envelope signal and a polarity signal.

In accordance with the above-described configuration, the polaritydetection accuracy does not decrease even in the case where the lightbeam is shifted with respect to a track center (i.e., an off-trackstate) the light beam in the present example. As a result, the presentexample makes it possible to accurately determine whether the light beamis on a land or a groove.

INDUSTRIAL APPLICABILITY

The optical disk of the present invention includes ID sections providedin a symmetrical manner in a middle position between a land and agroove. As a result, the positions and polarities of the ID sections canbe detected with high accuracy even in the case where the reproductionlight beam is offset or where the reproduced signal has dropouts. Thus,according to the present invention, the generation of a read gate as areading reference and the identification of lands and grooves becomestable, thereby greatly improving the reliability of the disk driveapparatus.

Another optical disk according to the present invention is capable ofrecording/reproduction on land tracks and groove tracks, and includessector addresses provided so as to be shifted in a middle positionbetween adjoining tracks. A plurality of address blocks constituting onesector address are grouped into address groups, where one group includesat least two or more address blocks; the address groups are disposed sothat each address group alternately wobbles toward the inner peripheryside and the outer periphery side with respect to a track center alongthe radius direction. Thus, the sector addresses can be securely readeven if the light spot is off-tracked. Furthermore, the disturbance intracking control due to level variation of a tracking error signal in asector address region can be reduced.

In still another optical disk according to the present invention,address groups are provided where one group includes at least two ormore address blocks, and a clock synchronization signal is added to thebeginning portion of each address block, the clock synchronizationsignal for the first address block of the address group being longerthan the clock synchronization signal for the other address block. Thus,the reproduction of the begging portion of the address group is stablyperformed. As a result, the synchronization with the read clock, thesetting of the slice level for digitization, and the like can besecurely performed. It is possible to properly demodulate the datarecorded in the portions which are called later than the portions inwhich the clock synchronization signal is recorded.

In accordance with an optical disk recording/reproduction apparatus ofthe present invention, when reproducing wobbled address blocks, theaddress numbers which have been read can be corrected in accordance withoverlapping sequential numbers, regardless of a land track or a groovetrack. As a result, different address numbers can be read for therespective address blocks within one sector address, whereby an accurateaddress value can be obtained.

In accordance with another optical disk recording/reproduction apparatusof the present invention, a true off-tracking amount between the lightspot and a track can be detected by detecting a difference between atracking error signal or a reflected light amount signal in addressblocks on the inner periphery side and a tracking error signal or areflected light amount signal in address blocks on the outer peripheryside. Furthermore, by correcting the tracking error signal using thisoff-tracking amount, a tracking control system can be realized which iscapable of positioning the light spot so as to be always on the trackcenter.

Thus, in accordance with another optical disk recording/reproductionapparatus of the present invention, a broad-band tracking error signalcontaining a high frequency component is detected in a tracking errordetection circuit, and an ID envelope signal is detected by using a highpass filter, a full-wave rectifier, a first low pass filter, and a firstcomparator, based solely on ID sections within a tracking error signal.At this time, even if the data written on a track other than in the IDsections is reproduced, its amplitude does not appear in the trackingerror signal detected by a differential amplifier, so that misdetectiondoes not occur.

In accordance with still another optical recording/reproductionapparatus of the present invention, the polarities of ID sectionsprovided in a symmetrical manner between a land and a groove aredetected by a second low pass filter, a third low pass filter, and asecond comparator. At this time, even if the tracking error signal hasan amplitude disturbance in an off-track state of the light beam, thedirection of the polarity signal generated by the second and third lowpass filters having different bands does not change. Moreover, since aread gate is generated from the envelope signal and the direction of thepolarity signal is determined in a period during which the envelopesignal is valid, it is possible to identify whether the light beam istracking on a land or a groove.

What is claimed is:
 1. An optical disk comprising a land track and agroove track, wherein each of the land track and the groove trackincludes a plurality of sectors, each of the plurality of sectorsincludes a sector address region and a data region, and the sectoraddress region includes a plurality of address blocks, further whereinthe sector address region includes a first address block group includinga plurality of address blocks immediately adjacent to each other in acircumferential direction and a second address block group including aplurality of address blocks immediately adjacent to each other in thecircumferential direction, each of the plurality of address blocksincluded in the first address block group includes an address number andan ID number, each of the plurality of address blocks included in thesecond address block group includes an address number and an ID number,the first address block group and the second address block group aredisposed so as to be shifted oppositely in a radial direction withrespect to a track central axis by substantially half of a track pitch,and non-pit data is located at the beginning and the end of each of theplurality of address blocks included in the first address block groupand the second address block group.
 2. An optical diskrecording/reproduction apparatus for an optical comprising a land trackand a groove track, wherein each of the land track and the groove trackincludes a plurality of sectors, each of the plurality of sectorsincludes a sector address region and a data region, and the sectoraddress region includes a plurality of address blocks, further whereinthe sector address region includes a first address block group includinga plurality of address blocks immediately adjacent to each other in acircumferential direction and a second address block group including aplurality of address blocks immediately adjacent to each other in thecircumferential direction, each of the plurality of address blocksincluded in the first address block group includes an address number andan ID number, each of the plurality of address blocks included in thesecond address block group includes an address number and an ID number,the first address block group and the second address block group aredisposed so as to be shifted oppositely in a radial direction withrespect to a track central axis by substantially half of a track pitch,and non-pit data is located at the beginning and the end of each of theplurality of address blocks included in the first address block groupand the second address block group, the apparatus comprising: an opticalhead for radiating a light beam on the optical disk and receivingreflected light from the optical disk to output a reproduced signal, anaddress signal reproduction section for reading the address number andthe ID number from each of the plurality of address blocks included inthe first address block group and the second address block group basedon the reproduced signal; and an address correction section forcorrecting the address number read from each of the plurality of addressblocks included in the first address block group and the second addressblock group in accordance with the ID number read from each of theplurality of address blocks included in the first address block groupand the second address block group.
 3. An optical disk comprising a landtrack and a groove track, wherein each of the land track and the groovetrack includes a plurality of sectors, each of the plurality of sectorsincludes a sector address region and a data region, and the sectoraddress region includes a plurality of address blocks, further whereinthe sector address region includes a first address block group includinga plurality of address blocks immediately adjacent to each other in acircumferential direction and a second address block group including aplurality of address blocks immediately adjacent to each other in thecircumferential direction, each of the plurality of address blocksincluded in the first address block group includes an address number andan ID number, each of the plurality of address blocks included in thesecond address block group includes an address number and an ID number,the first address block group and the second address block group aredisposed so as to be shifted oppositely in a radial direction withrespect to a track central axis by substantially half of a track pitch,and non-pit data is located at the beginning and the end of the firstaddress block group and non-pit data is located at the beginning and theend of the second address block group.
 4. An optical diskrecording/reproduction apparatus for an optical disk comprising a landtrack and a groove track, wherein each of the land track and the groovetrack includes a plurality of sectors, each of the plurality of sectorsincludes a sector address region and a data region, and the sectoraddress region includes a plurality of address blocks, further whereinthe sector address region includes a first address block group includinga plurality of address blocks immediately adjacent to each other in acircumferential direction and a second address block group including aplurality of address blocks immediately adjacent to each other in thecircumferential direction, each of the plurality of address blocksincluded in the first address block group includes an address number andan ID number, each of the plurality of address blocks included in thesecond address block group includes an address number and an ID number,the first address block group and the second address block group aredisposed so as to be shifted oppositely in a radial direction withrespect to a track central axis by substantially half of a track pitch,and non-pit data is located at the beginning and the end of the firstaddress block group and non-pit data is located at the beginning and theend of the second address block group, the apparatus comprising: anoptical head for radiating a light beam on the optical disk andreceiving reflected light from the optical disk to output a reproducedsignal, an address signal reproduction section for reading the addressnumber and the ID number from each of the plurality of address blocksincluded in the first address block group and the second address blockgroup based on the reproduced signal; and an address correction sectionfor correcting the address number read from each of the plurality ofaddress blocks included in the first address block group and the secondaddress block group in accordance with the ID number read from each ofthe plurality of address blocks included in the first address blockgroup and the second address block group.